Abstract

The reaction of iron(II1) hydroxide with alkali-metal or ammonium fluoride and 48% hydrofluoric acid in the presence of hydrogen peroxide, followed by the addition of ethanol, directly gives alkali-metal or ammonium hexafluoroferrates(III), A3FeF6 (A = Na, K, or NH4), in very high yields. An investigation of the reaction of ammonium or potassium thiocyanate and 48% HF with iron(II1) hydroxide in the presence of hydrogen peroxide has been carried out. Sulfate has been obtained as the oxidation product of SCN-, without involving reduction of iron(II1) and providing an access to fluoro(sulfato)ferrates(III) of the types (NH4)2[Fe(SO4)F3J and K3[Fe(SO4)F4]. Similar reactions with sulfates in lieu of thiocyanates, either in the presence of or in the absence of H202, do not afford fluoro(sulfato)ferrates(III), however. IR spectroscopy and laser Raman spectroscopy provide evidence for a chelated sulfate in each of the fluoro(sulfato)ferrates(III).